Internal combustion engine power output is limited by a number of factors, one being heat. When the temperature of the combustion chamber reaches a certain level, the fuel-air mixture in the chamber may spontaneously combust (which is also known as “pre-ignition”). If the ignition device (such as a sparkplug) subsequently ignites, “knocking” may occur, leading to severe engine damage, such as, bending rods and damaging pistons. The likelihood of knocking increases as engine temperatures increase.
Engine temperatures increase with an increase in combustion chamber pressure. Combustion chamber pressure is substantially increased by adding a turbocharger or a supercharger to an engine. These devices create “boost”, or engine power, by compressing the air entering the combustion chamber. Increasing chamber pressure leads to increased power output. All this increased pressure, however, increases the heat in the chamber, which, when aggressive ignition timing is incorporated, knocking may also occur at a higher rate.
Under this scenario, cooling the combustion chamber to decrease or eliminate pre-ignition is therefore highly desirable. Cooling not only leads to a decrease in the likelihood of severe engine component damage, but it decreases overall engine wear. Additionally, many aspects of engine performance are increased.
Engine cooling may be done via an intercooler. In one type of intercooler, ambient air is directed onto the intercooler device (similar to a radiator), cooling the intercooler core. The core may be co-located with radiators adapted to use cooling fluids to cool engine parts. Heat is transferred between the radiator fluid and the intercooler core to keep the engine cool. Many intercoolers add substantial weight to the engine, or are complex to install and maintain, and are therefore expensive. Therefore, other engine cooling methods have been developed.
During the Second World War, a mixture of water and methanol was used to cool aircraft engines. To do so, the mixture was added into the fuel and air that was entering the combustion chamber. Upon contacting the fuel-air mixture, water was found to cool the mixture. Cooling the mixture not only decreases knocking, but it also typically allows for more mixture to enter the cylinder. Therefore, a higher output charge is created since more fuel enters the chamber, creating an increase in performance.
During combustion, when injecting a water-methanol mixture, the mixture further reduces combustion chamber heat by absorbing heat from the exploding fuel-air mixture, with the water using the heat energy to convert from liquid to gas. Therefore, the heat energy released directly into the chamber is decreased. Reducing the temperature of the chamber reduces the potential for pre-ignition and knocking. Additionally, transforming the water into steam increases chamber pressure, which also increases power output. A water-methanol mixture is used because methanol's high octane rating decreases the likelihood that knocking and pre-ignition will occur, and because methanol combusts, it adds increased power to the chamber than what water alone can provide.
A severe problem created by water-alcohol injection systems, including water-methanol injection systems occurs when an incorrect amount of mixture is injected into the combustion chamber. This may occur when an injection line is blocked, or a mixture reservoir is depleted, or otherwise. Without a proper amount of water-methanol, the chamber is not properly cooled and pre-injection and knocking will likely occur at an increased rate during a turbocharged or supercharged state with aggressive timing, causing disastrous effects on an engine and requiring significant engine part replacement.
Current water-methanol injection systems do not properly address the problem of protecting engine components during injection-flow failure, and are limited in their use. For example, automobile injection systems are designed to run at a maximum air-fuel flow rates of 450 ml/min, which limits their use to 400 hp systems or below. Also, if the actual methanol-water flow rate from the pump is lower than what the water injection controller signals the pump to release for a specific boost level, engine damage may occur since the combustion chamber may not be cooled enough.
Some current injection systems are also deficient because they use a constant electronic signal to aggressively tune the system which, over time, may reduce the effectiveness of signal receptors such as solenoids and relays, thereby reducing the effectiveness of the entire injection system. Lastly, when flow rate drops, the injection system will immediately trigger the boost controller to dial back boost or open a wastegate so pressure is not increased in the chamber. In some systems, this may occur prematurely. For example, a false trigger may be given due to a false flowrate reading when a bump in the road accidentally drops water flow for a brief period.